The present invention relates to a signal device for fishing rods which can send out signals to cause the angler to notice a fish is hooked. An angler always has to keep an eye on the float in order to react immediately when a fish is hooked and has hence less time to relax. When fishing in the dark or casting hook far away from the edge to catch bigger fish, the float can hardly be seen. Therefore, an angler can only feel a shaking of the fishing rod by hand when a fish is hooked. It is not easy to make a correct judgement in such manner.